Hydrogen is a very attractive fuel because it is clean and can be used to efficiently produce electricity in a fuel cell. The automotive industry expends significant resources in the development of hydrogen fuel cells as a source of power for vehicles. Such vehicles would be more efficient and generate fewer emissions than today's vehicles employing internal combustion engines.
A (PEM) Proton Exchange Membrane fuel cell employs a solid polymer as an electrolyte membrane in a commonly adopted fuel cell. In this type of fuel cell vehicle, power generation is carried out by the electrochemical reaction between air and hydrogen within the fuel cell. A hydrogen fuel cell is an electro-chemical device that includes an anode and a cathode with an electrolyte disposed therebetween. The anode receives hydrogen gas and the cathode receives oxygen or air. The hydrogen gas is disassociated in the anode to generate free hydrogen protons and electrons. The hydrogen protons pass through the electrolyte to the cathode. The hydrogen protons react with the oxygen and the electrons in the cathode to generate water. The electrons from the anode cannot pass through the electrolyte, and thus, are directed through a load to perform work before being sent to the cathode. The work acts to operate the vehicle.
Many fuel cells are typically combined in a fuel cell stack to generate the desired power for the vehicle. The fuel cell stack receives a cathode input gas as a flow of air, typically forced through the stack by a compressor. Not all of the oxygen in the air is consumed by the stack, and some of the air is outputted as a cathode exhaust gas that may include water as a stack by-product. The air not used for the power generation is externally exhausted through an exhaust pipe together with water created by the electrochemical reaction. Further, since the fuel cell is supplied with high pressure air, the high pressure exhaust gas flows through the exhaust pipe.
PEM fuel cells operate at low temperatures. Ambient pressure designs operate near 80° C. This level is much lower than the over 2000° C. flame temperature and roughly 500° C. exhaust gas temperature of a gasoline combustion engine. Pressurized PEM fuel cells use only relatively low pressures, so temperatures are under 200° C. Some of this heat is carried away in the exhaust stream.
The components of a fuel cell vehicle exhaust system may include a fuel cell stack exhaust pipe attached to a fuel cell stack, such as the hydrogen PEM fuel cell described above. The fuel cell exhaust pipe acts as a conduit between the fuel cell stack and the fuel cell exhaust system. The fuel cell exhaust travels from the fuel cell stack through the exhaust pipe to additional components such as an air diffuser and the exhaust tubes into the atmosphere. The support structure for the exhaust system includes a pipe for routing the exhaust and a series of hangers for supporting the pipe. Ground clearance of the hanging pipe is a design consideration along with exhaust noise and general exposure of the exhaust system to the atmosphere.
It would be desirable to provide a temperature tolerant exhaust system that eliminates the need for exhaust pipes, pipe routing, support systems, and ground clearance issues.